Magnetostatic wave devices for high frequency signal processing

Details Magnetostatic wave devices for high frequency signal processing Magnetostatic wave devices for high frequency signal processing

2000-01-28

2002-03-12

Pascal, Robert (Department: 2817)

Wave transmission lines and networks

Coupling networks

Delay lines including elastic bulk wave propagation means

C333S158000, C333S195000, C333S201000, C333S202000, C310S026000

Reexamination Certificate

active

06356165

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to magnetostatic wave devices for processing high frequency signals; and, more particularly, to devices, which is capable of reducing a variation for each of frequencies within a pass band.
DESCRIPTION OF THE PRIOR ART
In the field of magnetostatic wave devices, a high frequency filter, a delay line, a resonator, and a correlator are implemented through the use of a magnetostatic wave in order to cope with high frequency signals. To implement the magnetostatic wave devices, input and output electrodes are provided on a magnetically active ferromagnetic thin film on a magnetically inactive dielectric substrate, or a ferromagnetic thin film is placed on the magnetically inactive dielectric substrate after the input and output electrodes are produced. An appropriate magnetic field is then applied for energy conversion and transmission. According to prior art, input and output electrodes are lines having same size or multiple lines. In case of multiple lines, a distance between neighboring lines is constant. For both cases, a variation of wavelength for each frequency in a desired pass band of the devices is not considered effectively, thereby providing a severe characteristic variation in the pass band. A ferromagnetic thin film is provided in one side of the magnetically inactive substrate. The ferromagnetic thin film is provided in both sides to adjust a group speed by employing magnetically different thin films. Further, there is no metal shield for electrically separating input and output portions, and a coupling between the input and output portions is generated outside the pass band, thereby transmitting energy which is not desired.
FIG. 1
illustrates a schematic diagram of a prior magnetostatic wave device shown from the top, and
FIG. 2
presents the prior magnetostatic wave device in
FIG. 1
shown from the front. As shown, the magnetostatic wave device includes an input transmission line
12
a
, an output transmission line
13
a
, an input energy conversion portion
12
b
, an output energy conversion portion
13
b
, and a magnetically active ferromagnetic substance
14
b
. The input and output lines
12
a
and
13
b
having a constant width are placed on one side of a dielectric substrate
11
whose the other side is grounded
16
. The input and output energy conversion portions
12
b
and
13
b
generating energy conversion between electromagnetic wave and magnetostatic wave are composed of multiple number of lines each of which has a constant width w
1
or w
3
, a length L
1
and distances g
1
, g
2
between neighboring lines (See FIG.
3
). The ferromagnetic substance
14
b
is provided on a magnetically active substrate
14
a.
When a magnetic field with a magnitude larger than saturated magnetization is applied to the magnetostatic wave device, the magnetically active ferromagnetic substance
14
b
is saturated. When an electromagnetic wave within the frequency band can be absorbed by the magnetized ferromagnetic substance is transmitted to the input energy conversion portion
12
b
, the electromagnetic wave is magnetically coupled and a magnetostatic wave is generated. The magnetostatic wave is transmitted to the output energy conversion portion
13
b
through the magnetized ferromagnetic substance and then re-converted to the electromagnetic wave, resulting in energy transmission.
A multi-layer structure
14
including the ferromagnetic substance
14
b
, and end portions
15
a
and
15
b
are illustrated in FIG.
1
.
Referring to
FIG. 3
, line structure of the input and output energy conversion portions
12
b
and
13
b
employed in the prior magnetostatic wave devices are illustrated. The energy conversion lines for electromagnetic wave and magnetostatic wave are single lines each having the constant width w
1
or w
3
in the direction of current flow, and multiple number of the single lines each having a length L
1
are placed with a constant distance g
1
or g
2
.
The conversion line described above is employed to select a specific frequency and is good at obtaining a narrow band characteristic. However, it lowers efficiency in selecting a specific frequency band, thereby distorting a pass band characteristic as shown in FIG.
31
. Further, since there is no means to block electromagnetic wave coupling between the input and output energy conversion portions, energy is also transmitted by a transmission of the magnetostatic wave as a frequency increase. Thus, the value outside the pass band becomes high as shown in
FIG. 31
, thereby degrading a frequency selectivity for the device.
In addition, when ground planes are placed with a constant distance at the magnetized ferromagnetic substance as shown in
FIG. 1
, a group delay characteristic related to a group speed of the magnetostatic wave is not linear, thereby generating phase error.
In accordance with the prior magnetostatic wave device described above, multiple number of lines which has a constant distance between neighboring lines are employed as the input and output electrodes, thereby providing a severe variation of characteristics within the pass band. In addition, in order to increase the pass band there is needed the ferromagnetic substance having a larger width.
Further, since there is no metal shield to electrically separate the input and output energy conversion portions, the input and output energy conversion portions are coupled outside the pass band, thereby generating a larger energy transmission.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide magnetostatic wave devices for processing high frequency signals, which is capable of reducing a variation within the pass band of the device and blocking energy transmission outside the pass band by reducing energy emission on non-magnetization.
Magnetostatic wave devices of the present invention comprises: input and output electrodes for including energy conversion pattern provided in a dielectric substrate; a multi-layer magnetic substance structure placed at an upper portion of the dielectric substrate, wherein magnetically active thin film is placed at both sides of a magnetically inactive substrate; an upper shield, composed of grounded conductor, for preventing the input and output electrodes from coupling; a lower shield provided at the dielectric substrate, wherein the substrate contain a hole with the same length as the upper shield, and walls of said hole are provided with conductor; a magnetostatic wave end portion, inserted into the dielectric substrate to be placed at both end plane of the multi-layer magnetic structure, for blocking the magnetostatic wave not to reflect therefrom; and a magnetostatic wave reflector, provided in the dielectric substrate as a line whose width vary, for reflecting and selecting a desired pass band before it reaches to the magnetostatic wave end portion.


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